Study On Anatomy Of Five Species Of Ligularia

In this study,five species of Ligularia were used as experimental materials: L.fischeri,L.fischeri‘Zijin’,L.villosum,L.schmidtii,and L.dentata ‘Desdemona’.The characteristics of its annual life history were observed by phenological period observation;The microscopic characteristics of seedcases were observed by scanning electron microscope(SEM),and the fruit,leaf,petiole,root and scape of five species of Ligularia were dissected by traditional paraffin section method.The anatomical characteristics of each organ were described in detail,and the relationship between anatomical characteristics and its ecological adaptability and evolution was deeply analyzed.In order to reveal the significance of micromorphology and anatomical characteristics in the systematic taxonomy of Ligularia,to lay a foundation for the determination of the taxonomic status of L.fischeri‘Zijin’ and L.villosum,and to provide the corresponding theoretical basis for the introduction,cultivation,domestication and garden application of Ligularia.The results are as follows:(1)Five species of Ligularia germinated in the middle and late April and began to enter the vegetative growth period.When the temperature increased in summer,it entered the bolting stage,and completed the reproductive growth before cooling down in autumn.All the tested Ligularia have the characteristics of cold-resistant annual life cycle.The life cycle of Ligularia varied from 149 to 180 days in 2021,While life cycle of L.schmidtii is relatively short,That of L.dentata ‘Desdemona’ is the longest.(2)The seeds of L.fischeri,L.villosum and L.schmidtii are oval,the seeds of L.fischeri‘Zijin’are narrow oval,and the seeds of L.dentata ‘Desdemona’ are linear.The color of seeds varies from light brown to dark brown among different species.The patterns of seed side,umbilicus and beak were different under electron microscope.The seed anatomical structure showed that the exocarp,mesocarp,seed coat,endosperm and cotyledon were in turn from the outside to the inside.The seed appearance,surface micromorphology and anatomical structure characteristics of the five tested species of Ligularia have obvious differences,which have important taxonomic significance.(3)L.fischeri,L.fischeri‘Zijin’,L.villosum and L.dentata ‘Desdemona’are all heterohedral leaves.Stomata are concentrated in the lower epidermis,and there are clearly differentiated palisade tissue and sponge tissue.Palisade tissue only exists on the side near the upper epidermis.The thickness of sponge tissue was higher than that of palisade tissue;The looseness of organizational structure is greater than the compactness of organizational structure;L.schmidtii is an isoplanar leaf with undifferentiated palisade tissue.The stomatal irregular type is evenly distributed in the upper and lower epidermis,and the mesophyll cells are irregular and loosely arranged.The data of leaf anatomical characteristics of five species of Ligularia showed that their ability to control water was weak,but the ability to tolerate shade was strong.The palisade tissue of L.fischeri ‘Zijin’is the thickest,with the highest density of tissue structure.The average thickness of palisade tissue is about twice that of L.fischeri,indicating that its palisade layer contains more chloroplasts,which can improve its photosynthetic efficiency and has the potential for high yield and disease resistance.(4)The transverse section of the main vein of L.villosum and L.dentata ‘Desdemona’ is obovate,the L.fischeri is nearly round,the L.fischeri ‘Zijin’ is nearly heart-shaped,and the L.schmidtii is inverted into triangle.Except that the main veins of L.villosum are infinite double tenacious vascular bundles,the rest are infinite outer tenacious vascular bundles.The petiole is composed of epidermis,basic tissue and vascular bundle.The epidermal cells are closely arranged,and there are several layers of thick horny tissue inside the epidermis.L.fischeri and L.dentata ‘Desdemona’ have pith structure in the central petiole.The types of vascular bundles in the petiole are all infinite outer tenacious vascular bundles.The vascular bundles of L.fischeri ‘Zijin’ and L.villosum are arranged in a "V" shape,the vascular bundles of L.fischeri are circular,and the vascular bundles of L.dentata ‘Desdemona’ are scattered in the basic tissues of the petiole.(5)The five species of Ligularia have no secondary root structure,and the primary root is composed of epidermis,cortex and stele,with secretory cavity and pulp.There are obvious differences in the composition and structure between different species.The primary xylem of L.fischeri is a four-archetype,the primary xylem of L.fischeri ‘Zijin’,L.villosum,and L.dentata‘Desdemona’ is a five-archetype,and the primary xylem of L.schmidtii is a multi-prototype;The primary xylem of L.fischeri can be seen with ring-shaped vessels,whorled vessels and pitted vessels,the primary xylem vessels of L.fischeri ‘Zijin’ and L.villosum vessels are pitted vessels,and the primary xylem of L.schmidtii can be seen with ring-shaped vessels and whorled vessels;L.dentata ‘Desdemona’duct type is threaded duct.(6)The five species of Ligularia scapes tested were divided into epidermis,cortex and vascular bundle from the outside to the inside,and the center of the scapes was a large area of pith.The epidermis is covered with a layer of cuticle with different thickness,and a small amount of stomatal structure can be seen on the epidermis.Except for L.schmidtii without epidermal hair,the other four species of Ligularia have epidermal hair structure.The inner side of the epidermis is composed of thick-horned tissue and parenchyma with different thickness.The thick-horned tissue plays a supporting role in providing upward support for the scape.The vascular tissue of the scape of five species of Ligularia is relatively developed,with two inner and outer rings.The diameter of the outer ring vascular bundle is larger than that of the inner ring vascular bundle.The number of inner ring vascular bundles of L.fischeri,L.fischeri‘Zijin’,L.villosum and L.dentata ‘Desdemona’ is greater than that of outer ring vascular bundles,and the number of outer ring vascular bundles of Ligularia hybrida is more than that of inner ring vascular bundles.To sum up,there are obvious differences in morphology and anatomy between the seeds and organs of L.fischeri ‘Zijin’and L.fischeri.It can be seen that the two are not the same plant,and L.fischeri ‘Zijin’ should be a new variety.The annual life history characteristics,micromorphology and anatomical morphological characteristics of L.villosum support that it should be a new species.The relationship between L.schmidtii and other Ligularia is quite different,and the genetic relationship is far away,which is relatively primitive.The other four species of Ligularia are more evolved.The problem of long germination time and inconsistent emergence of seeds of L.schmidtii is related to its fruit volume and anatomical structure.The tested Ligularia has good cold tolerance and negative tolerance.The results of annual life history characteristics show that the flowering period of the five species of Ligularia lasts 1 to2 months,and the flowers are bright and beautiful,with strong ornamental effect.It is a fabulous plant resource for creating a sea of flowers and landscaping.Further studies on five species of Ligularia can be carried out at the molecular level.